gh-135056: Simplify args.header processing.

Author: aisipos

Lib/http/server.py

@@ -1055,10 +1055,6 @@ def _main(args=None):
         except OSError as e:
             parser.error(f"Failed to read TLS password file: {e}")
 
-    response_headers = []
-    for header, value in args.header or []:
-        response_headers.append((header, value))
-
     # ensure dual-stack is not disabled; ref #38907
     class DualStackServerMixin:
 
@@ -1072,7 +1068,7 @@ def server_bind(self):
         def finish_request(self, request, client_address):
             self.RequestHandlerClass(request, client_address, self,
                                      directory=args.directory,
-                                     response_headers=response_headers)
+                                     response_headers=args.header)
 
     class HTTPDualStackServer(DualStackServerMixin, ThreadingHTTPServer):
         pass

Lib/test/test_httpservers.py

@@ -1505,7 +1505,7 @@ def test_response_headers_arg(self):
                 mock_handler_init.assert_called_once_with(
                     mock.ANY, mock.ANY, mock.ANY, directory=mock.ANY,
                     response_headers=[
-                        ('Set-Cookie', 'k=v'), ('Set-Cookie', 'k2=v2')
+                        ['Set-Cookie', 'k=v'], ['Set-Cookie', 'k2=v2']
                     ]
                 )